use nu_ansi_term::{Gradient, Rgb, build_all_gradient_text, gradient::TargetGround};
use nu_engine::command_prelude::*;

#[derive(Clone)]
pub struct SubCommand;

impl Command for SubCommand {
    fn name(&self) -> &str {
        "ansi gradient"
    }

    fn signature(&self) -> Signature {
        Signature::build("ansi gradient")
            .named(
                "fgstart",
                SyntaxShape::String,
                "foreground gradient start color in hex (0x123456)",
                Some('a'),
            )
            .named(
                "fgend",
                SyntaxShape::String,
                "foreground gradient end color in hex",
                Some('b'),
            )
            .named(
                "bgstart",
                SyntaxShape::String,
                "background gradient start color in hex",
                Some('c'),
            )
            .named(
                "bgend",
                SyntaxShape::String,
                "background gradient end color in hex",
                Some('d'),
            )
            .rest(
                "cell path",
                SyntaxShape::CellPath,
                "For a data structure input, add a gradient to strings at the given cell paths.",
            )
            .input_output_types(vec![
                (Type::String, Type::String),
                (
                    Type::List(Box::new(Type::String)),
                    Type::List(Box::new(Type::String)),
                ),
                (Type::table(), Type::table()),
                (Type::record(), Type::record()),
            ])
            .allow_variants_without_examples(true)
            .category(Category::Platform)
    }

    fn description(&self) -> &str {
        "Add a color gradient (using ANSI color codes) to the given string."
    }

    fn run(
        &self,
        engine_state: &EngineState,
        stack: &mut Stack,
        call: &Call,
        input: PipelineData,
    ) -> Result<PipelineData, ShellError> {
        operate(engine_state, stack, call, input)
    }

    fn examples(&self) -> Vec<Example<'_>> {
        vec![
            Example {
                description: "draw text in a gradient with foreground start and end colors",
                example: "'Hello, Nushell! This is a gradient.' | ansi gradient --fgstart '0x40c9ff' --fgend '0xe81cff'",
                result: None,
            },
            Example {
                description: "draw text in a gradient with foreground start and end colors and background start and end colors",
                example: "'Hello, Nushell! This is a gradient.' | ansi gradient --fgstart '0x40c9ff' --fgend '0xe81cff' --bgstart '0xe81cff' --bgend '0x40c9ff'",
                result: None,
            },
            Example {
                description: "draw text in a gradient by specifying foreground start color - end color is assumed to be black",
                example: "'Hello, Nushell! This is a gradient.' | ansi gradient --fgstart '0x40c9ff'",
                result: None,
            },
            Example {
                description: "draw text in a gradient by specifying foreground end color - start color is assumed to be black",
                example: "'Hello, Nushell! This is a gradient.' | ansi gradient --fgend '0xe81cff'",
                result: None,
            },
        ]
    }
}

fn value_to_color(v: Option<Value>) -> Result<Option<Rgb>, ShellError> {
    let s = match v {
        None => return Ok(None),
        Some(x) => x.coerce_into_string()?,
    };
    Ok(Some(Rgb::from_hex_string(s)))
}

fn operate(
    engine_state: &EngineState,
    stack: &mut Stack,
    call: &Call,
    input: PipelineData,
) -> Result<PipelineData, ShellError> {
    let fgstart: Option<Value> = call.get_flag(engine_state, stack, "fgstart")?;
    let fgend: Option<Value> = call.get_flag(engine_state, stack, "fgend")?;
    let bgstart: Option<Value> = call.get_flag(engine_state, stack, "bgstart")?;
    let bgend: Option<Value> = call.get_flag(engine_state, stack, "bgend")?;
    let column_paths: Vec<CellPath> = call.rest(engine_state, stack, 0)?;

    let fgs_hex = value_to_color(fgstart)?;
    let fge_hex = value_to_color(fgend)?;
    let bgs_hex = value_to_color(bgstart)?;
    let bge_hex = value_to_color(bgend)?;
    let head = call.head;
    input.map(
        move |v| {
            if column_paths.is_empty() {
                action(&v, fgs_hex, fge_hex, bgs_hex, bge_hex, head)
            } else {
                let mut ret = v;
                for path in &column_paths {
                    let r = ret.update_cell_path(
                        &path.members,
                        Box::new(move |old| action(old, fgs_hex, fge_hex, bgs_hex, bge_hex, head)),
                    );
                    if let Err(error) = r {
                        return Value::error(error, head);
                    }
                }
                ret
            }
        },
        engine_state.signals(),
    )
}

fn action(
    input: &Value,
    fg_start: Option<Rgb>,
    fg_end: Option<Rgb>,
    bg_start: Option<Rgb>,
    bg_end: Option<Rgb>,
    command_span: Span,
) -> Value {
    let span = input.span();
    match input {
        Value::String { val, .. } => {
            match (fg_start, fg_end, bg_start, bg_end) {
                (None, None, None, None) => {
                    // Error - no colors
                    Value::error(
                        ShellError::MissingParameter {
                            param_name:
                                "please supply foreground and/or background color parameters".into(),
                            span: command_span,
                        },
                        span,
                    )
                }
                (None, None, None, Some(bg_end)) => {
                    // Error - missing bg_start, so assume black
                    let bg_start = Rgb::new(0, 0, 0);
                    let gradient = Gradient::new(bg_start, bg_end);
                    let gradient_string = gradient.build(val, TargetGround::Background);
                    Value::string(gradient_string, span)
                }
                (None, None, Some(bg_start), None) => {
                    // Error - missing bg_end, so assume black
                    let bg_end = Rgb::new(0, 0, 0);
                    let gradient = Gradient::new(bg_start, bg_end);
                    let gradient_string = gradient.build(val, TargetGround::Background);
                    Value::string(gradient_string, span)
                }
                (None, None, Some(bg_start), Some(bg_end)) => {
                    // Background Only
                    let gradient = Gradient::new(bg_start, bg_end);
                    let gradient_string = gradient.build(val, TargetGround::Background);
                    Value::string(gradient_string, span)
                }
                (None, Some(fg_end), None, None) => {
                    // Error - missing fg_start, so assume black
                    let fg_start = Rgb::new(0, 0, 0);
                    let gradient = Gradient::new(fg_start, fg_end);
                    let gradient_string = gradient.build(val, TargetGround::Foreground);
                    Value::string(gradient_string, span)
                }
                (None, Some(fg_end), None, Some(bg_end)) => {
                    // missing fg_start and bg_start, so assume black
                    let fg_start = Rgb::new(0, 0, 0);
                    let bg_start = Rgb::new(0, 0, 0);
                    let fg_gradient = Gradient::new(fg_start, fg_end);
                    let bg_gradient = Gradient::new(bg_start, bg_end);
                    let gradient_string = build_all_gradient_text(val, fg_gradient, bg_gradient);
                    Value::string(gradient_string, span)
                }
                (None, Some(fg_end), Some(bg_start), None) => {
                    // Error - missing fg_start and bg_end
                    let fg_start = Rgb::new(0, 0, 0);
                    let bg_end = Rgb::new(0, 0, 0);
                    let fg_gradient = Gradient::new(fg_start, fg_end);
                    let bg_gradient = Gradient::new(bg_start, bg_end);
                    let gradient_string = build_all_gradient_text(val, fg_gradient, bg_gradient);
                    Value::string(gradient_string, span)
                }
                (None, Some(fg_end), Some(bg_start), Some(bg_end)) => {
                    // Error - missing fg_start, so assume black
                    let fg_start = Rgb::new(0, 0, 0);
                    let fg_gradient = Gradient::new(fg_start, fg_end);
                    let bg_gradient = Gradient::new(bg_start, bg_end);
                    let gradient_string = build_all_gradient_text(val, fg_gradient, bg_gradient);
                    Value::string(gradient_string, span)
                }
                (Some(fg_start), None, None, None) => {
                    // Error - missing fg_end, so assume black
                    let fg_end = Rgb::new(0, 0, 0);
                    let gradient = Gradient::new(fg_start, fg_end);
                    let gradient_string = gradient.build(val, TargetGround::Foreground);
                    Value::string(gradient_string, span)
                }
                (Some(fg_start), None, None, Some(bg_end)) => {
                    // Error - missing fg_end, bg_start, so assume black
                    let fg_end = Rgb::new(0, 0, 0);
                    let bg_start = Rgb::new(0, 0, 0);
                    let fg_gradient = Gradient::new(fg_start, fg_end);
                    let bg_gradient = Gradient::new(bg_start, bg_end);
                    let gradient_string = build_all_gradient_text(val, fg_gradient, bg_gradient);
                    Value::string(gradient_string, span)
                }
                (Some(fg_start), None, Some(bg_start), None) => {
                    // Error - missing fg_end, bg_end, so assume black
                    let fg_end = Rgb::new(0, 0, 0);
                    let bg_end = Rgb::new(0, 0, 0);
                    let fg_gradient = Gradient::new(fg_start, fg_end);
                    let bg_gradient = Gradient::new(bg_start, bg_end);
                    let gradient_string = build_all_gradient_text(val, fg_gradient, bg_gradient);
                    Value::string(gradient_string, span)
                }
                (Some(fg_start), None, Some(bg_start), Some(bg_end)) => {
                    // Error - missing fg_end, so assume black
                    let fg_end = Rgb::new(0, 0, 0);
                    let fg_gradient = Gradient::new(fg_start, fg_end);
                    let bg_gradient = Gradient::new(bg_start, bg_end);
                    let gradient_string = build_all_gradient_text(val, fg_gradient, bg_gradient);
                    Value::string(gradient_string, span)
                }
                (Some(fg_start), Some(fg_end), None, None) => {
                    // Foreground Only
                    let gradient = Gradient::new(fg_start, fg_end);
                    let gradient_string = gradient.build(val, TargetGround::Foreground);
                    Value::string(gradient_string, span)
                }
                (Some(fg_start), Some(fg_end), None, Some(bg_end)) => {
                    // Error - missing bg_start, so assume black
                    let bg_start = Rgb::new(0, 0, 0);
                    let fg_gradient = Gradient::new(fg_start, fg_end);
                    let bg_gradient = Gradient::new(bg_start, bg_end);
                    let gradient_string = build_all_gradient_text(val, fg_gradient, bg_gradient);
                    Value::string(gradient_string, span)
                }
                (Some(fg_start), Some(fg_end), Some(bg_start), None) => {
                    // Error - missing bg_end, so assume black
                    let bg_end = Rgb::new(0, 0, 0);
                    let fg_gradient = Gradient::new(fg_start, fg_end);
                    let bg_gradient = Gradient::new(bg_start, bg_end);
                    let gradient_string = build_all_gradient_text(val, fg_gradient, bg_gradient);
                    Value::string(gradient_string, span)
                }
                (Some(fg_start), Some(fg_end), Some(bg_start), Some(bg_end)) => {
                    // Foreground and Background Gradient
                    let fg_gradient = Gradient::new(fg_start, fg_end);
                    let bg_gradient = Gradient::new(bg_start, bg_end);
                    let gradient_string = build_all_gradient_text(val, fg_gradient, bg_gradient);
                    Value::string(gradient_string, span)
                }
            }
        }
        other => {
            let got = format!("value is {}, not string", other.get_type());

            Value::error(
                ShellError::TypeMismatch {
                    err_message: got,
                    span: other.span(),
                },
                other.span(),
            )
        }
    }
}

#[cfg(test)]
mod tests {
    use super::{SubCommand, action};
    use nu_ansi_term::Rgb;
    use nu_protocol::{Span, Value};

    #[test]
    fn examples_work_as_expected() {
        use crate::test_examples;

        test_examples(SubCommand {})
    }

    #[test]
    fn test_fg_gradient() {
        let input_string = Value::test_string("Hello, World!");
        let expected = Value::test_string(
            "\u{1b}[38;2;64;201;255mH\u{1b}[38;2;76;187;254me\u{1b}[38;2;89;174;254ml\u{1b}[38;2;102;160;254ml\u{1b}[38;2;115;147;254mo\u{1b}[38;2;128;133;254m,\u{1b}[38;2;141;120;254m \u{1b}[38;2;153;107;254mW\u{1b}[38;2;166;94;254mo\u{1b}[38;2;179;80;254mr\u{1b}[38;2;192;67;254ml\u{1b}[38;2;205;53;254md\u{1b}[38;2;218;40;254m!\u{1b}[0m",
        );
        let fg_start = Rgb::from_hex_string("0x40c9ff".to_string());
        let fg_end = Rgb::from_hex_string("0xe81cff".to_string());
        let actual = action(
            &input_string,
            Some(fg_start),
            Some(fg_end),
            None,
            None,
            Span::test_data(),
        );
        assert_eq!(actual, expected);
    }
}
